Method of drying air for metallurgical uses.



W. WENSE.

METHOD OF'DRYING AIR FOR METALLURGICAL USES.

APPLICATION FILED JUNE 13. 1912.

1,169,371 Patented Jan. 25, 1916.

. ing is a specification.

uni.

WILHELM WENSE, 0F GRIESHEIM-ON-THE-MAIN, GERMANY, ASSIGNOR 'IO CHEMISCHE FABRIK GRIESHEIM-ELEKTRON,

rormrron or GERMANY.

0F FRANKFORT-ON-THE-MAIN, GERMANY, A COR- mn'rnon or DRYING AIR non METALLURGICAL nsns.

Specification of Letters Patent.

Patented Jan. 25, 1916.

Application filed June 13, 1912. Serial No. 703,540.

To all whom it may concern Be it known that I, JVJILHELM Wnivsn, a

subject of the Emperor of Germany, and resident of Griesheim-on-the-Main, Germany, have invented certain new and useful Improvements in Methods of Drying Air for Metallurgical Uses, of which the follow- This invention has for its object to provide eflicient and economical means for obtaining dry air for supply to blast furnaces and other like furnaces. 9

Within recent years it has been found that theme of dry air in blast furnaces for the production of iron presents great advantages as regards the consumptlon of fuel and the maintenance of the production and that the working of blast furnaces is thereby rendered uniform. For drying air the following means have, as far as is known hitherto been tried on a large scale, or are used practically. 1. Concentrated sulfuric acid.-According to Harrison (Ukcmz'schc Zez'tung 1911,

560) this has not been'successful,.as owing to its corrosive effects, sulfuric acid re-v quires a costly installation and the reconcentration of the acid-is very expensive.

2. Calcium ckZorz'd.' This is used at Differdingen but from data given in Stahl and Eisen for 18 May 1911 it is seen that the use of calcium chlorid requires a large installation and inconvenientperiodic working, as it is clear that the air s In contact with the stationary solidmaterlal 1n pieces I for a much longer time'than is the case with a liquid which is capable of belng finely dlstributed and readily kept in motion, and that the employment of calcium chlorid therefore involves the use of drymg'apparatus of very large dimensions.

3. Anhydrous sulfates used according to Harbords German specification No.

203,087 of 1.907. -Nothing is known about the use'of these in practical work and it does not appear to have been applied commercially. p

4. Cooling the air down to 5 centigradc according to GayZey.'-Many large works already work accprding to this process. It implies however a very large installation and is expensive in operation (Zeitschr/"t des Vereins Deutscher Ingenz'cure, 1909, 77).

I have found that the air for supply to blast and other like furnaces can be very economically and satisfactorily dried by means of strong solutions of either caustic soda, or caustic potash. Solid alkali has already been used as a drying material for gas for other purposes, but for drying air for blast and other like furnaces advantageous results have not been obtained by its use, but solutions of caustic soda, or potash, give much better results although they have in themselves less drying effect than solid alkalis. The drying action of such solutions is however sufiicient notwithstanding the speed at which the air must be passed through such solutions. The fact that it is possible to dry air rapidly and to a very great extent for the working of blast or other like furnaces by means of solutions of caustic soda, or potash, has not hitherto been known. In technical literature no data are to be found as to the pressure of the vapor of alkaline solutions required in the case of air for blast or other like furnaces. Lescoeur (Uomptes Rendus 103, 1260) and Fittica (Jahresberickte fu'r anemic, 1886', 1, 151) give for soda and potash a figure for temperatures between 0 and 30 centigrade, namely for 20 centigrade, but only for the extreme case of fully saturated solutions which are not generally suitable for employment on account of technical objections to the use of such strong solutions. Although the alkali solutions do not produce as high a drying'action as sulphuric acid, or calcium chlorid, it is nevertheless possible, for the purposes of this invention, to obtain a better result with solutions of causticsoda, or potash, than with the Gayley process which has met with some success in practice,

Water content of the dried air e5 Caustic solution. Temperature. gg gg g f 760 mm. pressure.

(1) 50.8 per cent. KOH; 1.2 13 centigrade. 1.11 to 1.25 grams.

per cent. K200 o 26 2.65 to 3.11 grams. (3) 49.0 per cent. M3011; 0.6 13 1.00 to 1.02 grams.

per cent. Na COM Do 26 2.38 to 2.42 grams.

From these figures it will be seen that the lower the temperature the more perfect is the drying. It is therefore advisable to cool the air and the solution to as low a temperature as it is economically practicable. The following is an example of how this invention can be carried out into practice, but the invention is of course not limited to this precise example. The air is treated with the solution of caustic soda, or potash, in towers, preferably in parallel currents, the air and solution being passed through several towers arranged in series, the first one being supplied with the more dilute solution already used in the other tower, or towers, while thelast tower is supplied with fresh solution. The reconcentration of the solutions can be effected inany suitable evaporating apparatus, for instance in open pans heated by gases from the blast, or other, furnace, or in multiple efi'ect evaporators operating under a vacuum. As the evaporation of the solution takes ace as hereinafter explained ,without any separation of salt, the process can be carried out with very simple apparatus.

The carbon dioxid contained in the air might, owing to the separation of carbonate, disturb the operation of the drying and evaporating apparatus because caustic alka-' line solutions, especially soda solution, can

hold but little dissolved carbonate. For this reason it is advisable to previously absorb the carbon dioxid from the air, which can be done in a special apparatus by any suitable, or known, method. This has the further advantage that lesser quantities of water have to be evaporated than when the carbon dioxid is allowed to be absorbed along with the water inthe drying apparatus. In both cases it is necessary to convert again much carbonate into caustic alkali (causticizing), which operation is only possible in dilute solution. In the first case however the more dilute solution can be used again directly for the absorption of the carbon dioxid, while in the second case the solutionshould be evaporated downto' about per cent. at least. The water content of the fresh air may be increased on it. being treated with the more dilute solution, as such solution, during the greater part of the year, has no drying, but a humidifying, action of the air. The working can however be so carried out (as it is possible to do without the complete causticizing operation inthe mode of working proposed) that the.

complete causticized solution is maintained at a strength at which it will cede considerably less water to the air than must be evaporated from the caustic solution in the other mode of working.

Caustic alkalis have over the drying means hithertoproposed also the incidental advantage that they remove also carbon dioxid from the air, this carbon dioxid, like water, requiring in blast furnace uselessly spent heat for decomposition by the incanportion of a tower G to which is admitted a solution of a suitable caustic alkali. The moisture removing solution is contained in a tank E which is suitably connected with the interior of the tower O, at different elevations, as through conduits and'pumping devices P. The dried air escapes from a pipe at the upper end of the tower which may be provided with an enlarged portion D communicating with the interior of the tower to receive any particles. of moisture that may be deposited therein. A'tank or receptacle F is provided to receive the saturated liquid flowing from the lower end ofthe tower C. Having thus described the invention what is claimed and desired to be secured by Letters-Patent is:

1. The hereindescribed method of drying air for metallurigcal uses, comprising exposing the air to the action of a strong solution of caustic alkali. 4

2. The hereindescribed method of drying air for metallurgical uses comprising preliminarily treating the air to remove carbon dioxid therefrom and subsequently exposing the air to .the' action of a solution'of caustic alkali.

air for metallurgical uses comprising circulating the air through a chamber in-which it I is subjected to the action of a. spray of a caustic alkali solution.

4. ,The hereindescribed method of drying i'zo 3. The hereindescribed method of drying.

air for metallurgical uses comprising circuname to this specification in the presence of lating the alir thrgugh a chanifber in whicl; it two subscribing witnesses. is subjecte to t e action 0 a spray o a. caustic alkali solution, the air and spray WILHELM WENSE' 5 moving through said chamber in opposite Witnesses:

directions. FRANZ HASSLAGHER,

In testimony whereof I have signed my MICHAEL VoLx. 

